1989 mustang gt, 5 speed manual. How do I find out what my rear gear ratio is? I just bought it about 3 weeks ago. Also, is there much difference in 3.55 and 3.73 gears? I've read all the posts and it seems most are comparing 3.73 to 4.10's. My car is a daily driver that does see the highway everyday. It seems a little slow on takeoff, but I have buried the 140 speedo on the highway. I would gladly sacrifice some top end for low end speed.